The invention relates to a method of continuously measuring the temperature of the surface of a strand over the length of a continuously cast strand, in particular a cast strand for steel slabs, within a roller guide of a continuous casting plant, wherein at least one thermoelement with its measuring junction and the thermocouple connecting the measuring junction with equalizing conduits are applied onto the strand surface and moved together with the strand surface.
It is known to use partial-radiation or two-color pyrometers in combination with sight tubes or light conductors for measuring the temperature of the strand surface. In this case, the pyrometer is arranged outside the cooling chamber of the continuous casting plant, a sight tube extending from the pyrometer to almost the surface of the strand. Since there is always steam within the cooling chamber, it is necessary, for keeping free the tube, to blow air in through the sight tube prior to and during measuring. This air, however, causes a cooling of the strand surface at the measuring point and thus a falsification of the measured result. With arcuate continuous casting plants, pyrometers that are arranged on the lower side of the strand, i.e., on the outer side of the arc, are particularly jeopardized by the penetration of water into the sight tube, a breakdown of the pyrometers often occurring after only a short measuring period. When using light conductors no cooling of the measuring point occurs, yet light conductors have only a low temperature resistance (up to about 240.degree. C.), and can be used only in limited lengths. Therefore, it is necessary to arrange the pyrometer in this case within the cooling chamber, which, however, constitutes quite a considerable risk to the functioning ability of the pyrometer.
When using a pyrometer, there is another disadvantage that the surface temperature of the strand can be measured on certain spots of the strand guide only. It is not possible with a pyrometer to continuously measure the temperature course of the surface, for instance, from the exit of the strand out of the mould as far as to the torch-cutting roller table. Such a continuous measuring is of a great significance, since thereby a faultless adjustment of the cooling of the strand in accordance with an optimal temperature course of the strand surface over the length of the plant is made possible.
It is known from German Offenlegungsschrift No. 26 57 068 to measure the surface temperature of the strand by means of a thermoelement applied onto the strand surface during the extraction of the strand from the mould, wherein the thermoelement, i.e., the measuring junction and the thermocouple connecting the measuring junction with the equalizing conduits, is applied onto the strand surface transversely to the longitudinal direction of the strand. This has the disadvantage that the point of connection of the thermoelement has to be within the cooling chamber, a short circuit due to humidity thus being possible. Moreover, it is necessary with the known method to move the connection point of the thermoelement synchronously with the strand, which requires a complex and expensive construction and involves the danger of this construction being damaged in the event of a strand breakthrough. In addition, the space laterally of the strand is rather limited.